Deep Brain Stimulators (DBS) have been found to be successful in treating a variety of neurological conditions, including, without limitation, movement disorders. Generally, such treatment involves placement of a deep brain stimulator type lead into a targeted region of the brain through a burr hole drilled in the patient's skull, and the application of appropriate stimulation through the lead to the targeted region.
Presently, in DBS, beneficial (symptom-relieving) effects are observed primarily at high stimulation frequencies above 100 Hz that are delivered in stimulation patterns or trains in which the interval between electrical pulses (the inter-pulse intervals) is constant over time. The beneficial effects of DBS on motor symptoms are only observed at high frequencies, while low frequency stimulation may exacerbate symptoms. See Benabid et al., 1991, and Limousin et al., 1995. Thalamic DBS at less than or equal to 50 Hz increases tremor in patients with essential tremor. See Kuncel et al. 2006. Similarly, 50 Hz DBS produces tremor in pain patients receiving simulation of the ventral posterior medial nucleus of the thalamus (VPM), but the tremor disappears when the frequency is increased. See Constantoyannis 2004. Likewise, DBS of the subthalamic nucleus (STN) at 10 Hz worsens akinesia in patients with Parkinson's disease (PD), while DBS at 130 Hz leads to significant improvement in motor function See Timmermann et al. 2004, and Fogelson et al. 2005. Similarly, stimulation of the globus pallidus (GP) at or above 130 Hz significantly improves dystonia, whereas stimulation at either 5 or 50 Hz leads to significant worsening. See Kupsch et al. 2003.
Model studies also indicate that the masking of pathological burst activity occurs only with sufficiently high stimulation frequencies. See Grill et al. 2004, FIG. 1. Responsiveness of tremor to changes in DBS amplitude and frequency are strongly correlated with the ability of applied stimuli to mask neuronal bursting. See Kuncel et al. 2007, FIG. 2.
Although effective, conventional high frequency stimulation generates stronger side-effects than low frequency stimulation, and the therapeutic window between the voltage that generates the desired clinical effect(s) and the voltage that generates undesired side effects decreases with increasing frequency. Precise lead placement therefore becomes important. Further, high stimulation frequencies increase power consumption. The need for higher frequencies and increased power consumption shortens the useful lifetime and/or increases the physical size of battery-powered implantable pulse generators. The need for higher frequencies and increased power consumption requires a larger battery size, and frequent charging of the battery, if the battery is rechargeable. As the stimulator portion of the DBS may be implanted into a patient, access to the leads, stimulator and the entirety of the DBS is often very difficult.
Once implanted into a patient, altering the battery or altering the stimulation of the system may preferably be avoided as surgery may be required to achieve such. It is desirable to limit the number of times that the implanted system is removed from the patient as every instance of surgery provides inherent risks that should generally be avoided.
However, there may be overriding benefits to alter some of the parameters of the stimulation applied to the patient, which may require altering parts of the system. Therefore, there is a need to alter the parameters of the DBS without requiring explanting of the DBS from the patient or other surgery.
The stimulation applied to the targeted region may be altered to improve the performance of the treatment. For example, a pattern of stimulation may be altered so as to improve the efficiency of the battery of the DBS, improve the efficacy of the treatment or both. However, not every patient reacts the same way to the stimulation. Accordingly, there is a need to be able to alter and manage the application of the stimulation to a specific patient or to treat a specific neurological condition. Further, there is a need to have a system that is easy to use for a clinician and patient. Further still, there is a need for a system that is programmable to alter the application of the stimulation.